1. Field of Invention
This invention pertains to the field of wheelchairs and more particularly to the field of seat cushions incorporating gel-filled envelopes for use in wheelchairs and the like.
2. Description of Related Art
Persons who are required to sit or recline in chairs, wheelchairs, recliners, or beds for long periods of time are prone to develop sores on those portions of their bodies where their body weight is borne. Users of wheelchairs are susceptible to these sores in the area of their buttocks and thighs due to the fact that nearly all of their weight is distributed over a relatively small area.
For this reason, wheelchair cushions have been developed to spread the weight of the person's body over a larger area and reduce the possibility of such sores. Among these seat cushions are those utilizing shaped trays. Such shaped trays are commonly made out of foam and are configured with recesses to receive various parts of the user's body, such as the buttocks region and the legs. In some designs, an envelope full of a flowable gel is utilized along with a shaped tray. In these designs, an envelope, usually elastomeric, is filled with a flowable gel material which is displaceable under the weight of the user's body.
Some examples of gel-filled envelopes include U.S. Pat. Nos. 4,842,330; 4,726,624; 4,588,229; 4,660,238; and 4,761,843, all to Jay. In addition, patents disclosing viscous, flowable, pressure compensating type gels used in products other than seat cushions include U.S. Pat. Nos. 4,243,754; 4,108,928; 4,144,658; 4,229,546; 4,255,202, all to Swann, Jr. and U.S. Pat. No. 3,402,411 to Hanson.
Although some of these designs performed adequately, improvements were desirable. For example, some of the gels incorporated in such elastomeric envelopes had a tendency to bleed through the envelope and stain fabric seat covers and the clothing of the wheelchair user. In addition, some gels were composed of two or more components and the components had a tendency to separate during the life of the product.
The present inventive seat cushion is a new and improved seat cushion which overcomes the foregoing difficulties and others while providing better and more advantageous overall results.